This invention relates to gas turbine engines and, more particularly, to a combustor assembly having a unique attachment between a ceramic combustor can and a metal fuel-air mixture section.
Conventional gas turbine engines, such as those used in aircraft, utilize a combustor to ignite a mixture of fuel and compressed air. Utilizing significant compressed air may further reduce the air available for combustor liner cooling and result in pressure loss during the cooling of the combustor liner. Such a lean mixture reduces the amount of air available to cool the combustor and increases the combustor temperature. Common by-products of fuel combustion are NOx and CO. To reduce NOx produced in the combustor, it is desirable to reduce the flame temperature. This requires a high percentage of compressed air to be mixed with the fuel to produce a lean fuel air mixture. For combustors made entirely of metal, the increase in temperature may exceed a desirable operating temperature of the metal.
To lower the cooling air requirement and the pressure loss, high temperature ceramic materials have been proposed for combustor liners. Disadvantageously, the coefficient of thermal expansion (CTE) of ceramics is typically much lower than that of metals, which may lead to thermal stress between parts made of ceramic and parts made of metal alloys. Furthermore, the difference in coefficients of the thermal expansion between ceramic and metal may render typical joining methods, such as welding or bonding, ineffective.
Accordingly, there is a need for a combustor assembly that provides and maintains a tight fit between a ceramic part and a metal part over a relatively wide temperature range.